Drug Decriminalization, Fentanyl, and Fatal Overdoses in Oregon

Key Points Question Is the 2021 Oregon law that decriminalized drug possession associated with overdose mortality when accounting for the spread of fentanyl through the state’s unregulated drug market? Findings In this cohort study of fatal overdose and fentanyl spread through Oregon’s unregulated drug market, decriminalization of drug possession was not associated with an increase in fatal drug overdose rates in Oregon in the 2 years after its enactment. Meaning The findings of this study suggest that when evaluating the association of public policies with overdose mortality, it is critical to account for the role of fentanyl as the principal driver of the overdose mortality epidemic in the US.

This table shows crude and adjusted results of the association of decriminalization on overdose mortality with three alternative panel data methods.The first pair of columns shows results from difference-in-differences (DID) two way fixed effect regressions; the second pair of columns shows results from the Interactive Fixed Effects (IFE) method, and the third pair shows results from the generalized synthetic control method (Gsynth).Following the approach we present in the main analyses, for each method, an unadjusted model including only an indicator for decriminalization is shown first, followed by a model that adjusts for fentanyl exposure.Estimates were conducted using the fect package in R.This figure shows the biannual count of samples containing fentanyl or a related substance (per 100,000 residents) in the NFLIS data, by state.The plot highlights the relative differences between states in the magnitude of samples, with some states (adjusting for population) contributing substantially more samples to NFLIS.This heterogeneity indicates the advantage of using the share of samples that contain fentanyl within each state (eFigure1), which adjusts for heterogeneity between states in their reporting practices to NFLIS.

Notes on Mortality Data
Specifically, we used the mortality codes Multiple Causes of Death (MCD) Drug/Alcohol Induced If decriminalization, rather than a regional fentanyl saturation, caused the observed increases in overdose deaths in these states, we might expect overdose mortality trends in Washington to deviate from Oregon after Washington re-criminalized drug possession.In Washington, drug decriminalization was in effect from February 25, 2021 to July 25, 2021.
We use the same Matrix Completion method as in the main analysis, but with monthly overdose mortality data, comparing the monthly change in overdose in Washington relative to an imputed counterfactual.These estimates are plotted in eFigure3, with the estimates prior to the decriminalization period shaded red, estimates during the decriminalization period shaded green, and estimates after the repeal of decriminalization shaded blue.As eFigure3 illustrates, trends in overdose deaths in Washington substantially accelerated after the state re-criminalized controlled substances.Overdose mortality increased to a much larger degree at the end of 2022more than a year after the legislature

eFigure 1 .
Fentanyl Exposure, by State, Over TimeStates are arranged by their approximate geographic location.The x-axis is the date in half-years from H1 2008 to H2 2022.The yaxis is the percent of all NFLIS seizures that contain a substance that NFLIS categorizes as "fentanyl or a related substance.eFigure 2. Within-State Associations Between Fentanyl Exposure and Overdose Mortality Rates by Region, 2008 to 2022 This Figure illustrates the relationship between the percent of all NFLIS law enforcement seizures that contain fentanyl and drug overdose mortality rates, with states roughly arranged geographically (via the geofacet R package).Each point represents a half-year period in a state over the period 2008-2022.In virtually all states, a strong positive relationship exists between fentanyl exposure and overdose mortality eFigure 3. Difference-in-Differences ResultsEffect of drug decriminalization on overdose mortality unadjusted, and adjusted for the rapid escalation of fentanyl by state This plot highlights the impact of adjusting for fentanyl on the estimated effect of decriminalization on overdose mortality.Blue point estimates and 95% confidence intervals replicate main effect differencein-difference results in Table1of Spencer 2023.Red point estimates and confidence intervals show the estimated treatment effect of decriminalization adjusting for the percent of fentanyl in NFLIS seizures.eFigure 4. Trend in Overdose Mortality in Washington State Before, During, and After Decriminalization This plot shows the trend in overdose mortality in Washington (relative to a synthetic control estimated through the Matrix Completion method without covariates) in the periods before the Blake decision decriminalized drugs (from January 2018 through February 2021; shaded red), during the 5-months of decriminalization (March 2021 through July 2021; shaded green), and in the months after drugs were decriminalized (August 2021 through December 2022; shaded blue).Each point represents the Average Treatment Effect on the Treated (ATT) for Washington in each month, with 95% confidence intervals.eFigure 5. Fentanyl Seizure Rates by State per Half Year(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020)(2021)(2022)

Causes:
Drug poisonings (overdose) Unintentional (X40-X44); Drug poisonings (overdose) Suicide (X60-X64); Drug poisonings (overdose) Homicide (X85); Drug poisonings (overdose) Undetermined (Y10-Y14).The 2022 death statistics were described as provisional.In replications of Spencer 2023, we used the following codes: Underlying Cause of Death (UCD) -Drug/Alcohol Induced Causes: Drug poisonings (overdose) Unintentional (X40-X44) Re-criminalization in Washington Both Oregon and Washington decriminalized simple possession of controlled substances in early 2021: in Oregon, M110, approved by the voters in November 2020, took effect February 1st, whereas Washington's state supreme court on February 25, 2021 struck down the statute criminalizing drugs in the decision State v Blake.The policy trajectories of the two states differed substantially thereafter, however.In April 2021, in response to the Blake decision, the Washington legislature passed two-year legislation (SB 5476) that restored criminal penalties for simple drug possession with an effective date of July 25, 2021 (the legislature later passed a permanent law criminalizing drug possession that took effect in 2023).Meanwhile, Oregon maintained decriminalization throughout the study period.
Trend in Overdose Mortality in Washington State Before, During, and After Decriminalization eFigure 5. Fentanyl Seizure Rates by State per Half Year (2008-2022) eMethods This supplementary material has been provided by the authors to give readers additional information about their work.eTable 1. Fentanyl Saturation (Per Capita Metric) and Overdose Rates

Table shows
coefficients, standard errors (SE), and confidence intervals (CI) of fentanyl exposure (operationalized as the inverse hyperbolic sine transform or asinh of fentanyl seizures per 100,000 people) on overdose death mortality rates.The unit of analysis is state-half (e.g., Alabama in H1 of 2010).Date range is

the percent of NFLIS records
Sensitivity Tests With Alternative Panel Data Models that were for what the laboratory defined as "fentanyl or related substances" and, second, the inverse hyperbolic sine transform of fentanyl seizures per capita) on overdose death mortality rates.Unit of analysis is state-half (e.g., Alabama in H1 of 2010).Date range is 2008 H1 to 2022 H2.Standard errors in parentheses.*impliesp < 0.05.Estimates were conducted using the fixest package in R. * p < 0.05.Jackknife standard errors in parentheses and confidence intervals in brackets.The Root Mean Square Error (RMSE), a measure of model fit, is shown to highlight the improved model fit in the model controlling for fentanyl.Estimates were conducted using the fect package in R.eTable 4.Standard errors in parenthesis.95% confidence intervals in brackets.* p < 0.05